1. Field of the Invention
In injectors for injecting fuel into combustion chambers of internal combustion engines, the high-pressure resistance of the injectors that can be used is primary. In existing injector designs whose housings include a separate nozzle inlet and a nozzle chamber surrounding the nozzle needle, and given the constantly increasing pressure level in the high-pressure collection chamber (common rail), their high-pressure resistance is becoming increasingly important in terms of their usability, and such injectors are reaching the limits to their high-pressure resistance.
2. Prior Art
German Patent DE 37 28 817 C2 relates to a fuel injection pump for internal combustion engines. The control valve member used in this fuel injection pump comprises a valve shaft, forming a guide sleeve and sliding in a conduit, and a valve head connected to the valve shaft and oriented toward the actuating device. The sealing face of the valve head cooperates with a face of the control bore that forms the valve seat. The valve shaft has a recess on its circumference, and the axial length of this recess extends from the orifice of the fuel supply line as far as the beginning of the valve head sealing face that cooperates with the valve seat, and in the recess, a face exposed to the pressure of the fuel supply line is formed. This face is equal in area to a face of the valve head that is exposed to the pressure of the fuel supply line, in the closed state of the control valve. As a result, in the closed state the valve is in pressure equilibrium; in addition, a spring element spring that loads the control valve toward its open position is disposed in the guide sleeve of the control valve member.
With the compact design proposed according to the invention of an injector for injecting fuel into combustion chambers of internal combustion engine, its high-pressure resistance can be increased considerably, since the nozzle supply line and the nozzle chamber, which surrounds the nozzle needle in the region of its discharge into the combustion chamber, can now be omitted. A much more compact design of an injector can thus be attained, which furthermore is considerably easier to manufacture from the standpoint of production technology. The nozzle needle in the injector configuration proposed according to the invention no longer takes on any sealing function. Guidance of the nozzle needle in the housing of the injector can therefore be provided without canting in guide regions, which can be smaller than in nozzle needle guides that also perform a sealing function. A smaller area can therefore be machined with higher surface quality, which has a positive effect on the production costs for the injector proposed according to the invention.
An integral embodiment of control parts and nozzle needle that are embodied as merging with one another makes it possible to dispose a spring element that generates high closing forces in the housing of the injector. As a result, the closing time of the nozzle needle on its seat can be favorably affected, so that the incident leakage losses in the injector proposed according to the invention, of compact design, can be kept within narrow limits.
Because fuel that is at extremely high pressure is delivered substantially vertically, and its inflow is into an annular gap surrounding the control part, incident pulsations or pressure fluctuations in the delivered fuel can be better damped, and in particular are not propagated during the injection phase, so that the shaping of the precisely defined injection course is unimpaired by pulsations in the fuel.
Another advantage intrinsic to the embodiment according to the invention is considered to be that the nozzle needle can be provided with inlet faces, by way of which fuel entering via the annular gap between the nozzle needle and the injector housing flows to the seat of the injection nozzle. The delivery of fuel through annular gaps is the primary way of achieving substantially greater high-pressure resistance of the injector proposed according to the invention, since the nozzle inlet and the nozzle chamber can be omitted. Besides the advantages of easier production and greater attainable durability, the elimination of the line system to the nozzle needle makes a substantially faster pressure buildup at the injection nozzle tip possible.